2007-11-12 08:28:12 · 7 answers · asked by papergir12 1 in Science & Mathematics ➔ Mathematics
21 + 3 i - 35 i - 5 i ²
21 - 32 i + 5
26 - 32 i
2007-11-16 05:10:59 · answer #1 · answered by Como 7 · 1⤊ 0⤋
I take it the question is just to simplify the expression.
Firstly you have to multiply out the brackets. When you do this, you multiply each term in the first bracket by each term in the second bracket, so
(3-5i)(7+i) = 3*7 + 3*i + (-5i)*7 + (-5i)*i = 21 + 3i -35i -5i^2
Now we can simplify slightly by combining the two terms with i in them, and by bearing in mind that i^2=-1
This gives 21 - 32i -5(-1) = 21 - 32i + 5 = 26 - 32i
2007-11-12 16:38:57 · answer #2 · answered by fi_trix29 2 · 0⤊ 0⤋
Use foil. 3*7 is 21. Then -5i*7 is -35i, 3*i is 3i. -5i*i equals -5i^2. i^2 is always -1, so it would be 5. When it is all added up it would by 26-32i.
Trust me this is the right answer, I wouldn't be in pre-calculus otherwise.
2007-11-12 16:36:03 · answer #3 · answered by sandboxjill2000 2 · 0⤊ 0⤋
(3-5i)(7+i)
21+3i-35i-5i^2 ( 5i squared)
-5i^2 = +5
21+5-32i
26-32i
2007-11-12 16:35:46 · answer #4 · answered by mm 2 · 1⤊ 0⤋
21 +3i-35i-5i^2
21 -32i-5i^2
2007-11-12 16:34:57 · answer #5 · answered by joyce 2 · 0⤊ 0⤋
21-32i-5i^2
2007-11-12 16:41:52 · answer #6 · answered by Sarika S 1 · 0⤊ 0⤋
21+3i-35i+5
26-32i
2007-11-12 16:32:14 · answer #7 · answered by UNIQUE 3 · 0⤊ 0⤋